共查询到20条相似文献,搜索用时 15 毫秒
1.
T. Ogasawara A. Yoshino H. Okabayashi C. J. O''Connor 《Colloids and surfaces. A, Physicochemical and engineering aspects》2001,180(3):317-322
In the 3-aminopropyltriethoxy silane–deuterated ethanol–H2O system, the rate of release of ethanol from the ethoxy groups, a reaction which occurs during the condensation process, has been followed by use of 1H NMR spectroscopy at different temperatures. Two separate reaction processes have been identified, and values of the reaction rate constants and thermodynamic parameters (Ea, ΔH‡ and ΔS‡) have been calculated. 相似文献
2.
H. Yano Y. Furukawa Y. Kuranaga K. Yamada T. Okuda 《Journal of Molecular Structure》2000,520(1-3):173-178
Powder X-ray diffraction, 119Sn NMR spectra, and 1H NMR spin–lattice relaxation times, T1, were measured for (CH3)nNH4−nSnCl3 (n=1–4). From the Rietveld analysis, it is shown that all four compounds crystallize into deformed perovskite-type structures at room temperature. The temperature dependence of 1H T1 was analyzed in terms of the CH3 reorientation and other motions of the whole cation. Except for the phase transition in CH3NH3SnCl3, which is from monoclinic to rhombohedral at 331 K, 1H T1 was continuously changed at other phase transitions in this compound as well as in the n=2–4 compounds, suggesting that the transitions are not caused by the change of the motional state of the cation but by an instability of the [SnCl3]nn− perovskite lattice. 相似文献
3.
The addition of t-butyl N,N-dibromocarbamate (BBC) to alkenes and cycloalkenes in the presence of BF3·Et2O proceeds smoothly at −20°C in CH2Cl2 affording upon reduction with aqueous Na2SO3 the corresponding β-bromo-N-Boc-amines. Immediate deprotection of these adducts with gaseous HCl yields β-bromoamine hydrochlorides in moderate yields. The regioselectivity typical for Markovnikov addition was observed for styrene. Stereospecific anti-addition of BBC to cyclohexene and (E)-hex-3-ene, as proven by 1H NMR evidence, is compatible with an ionic addition pathway and can be rationalized by assuming the intermediate complex formation between BBC and BF3. 相似文献
4.
J zsef Kaizer R bert Csonka G bor Speier 《Journal of molecular catalysis. A, Chemical》2002,180(1-2):91-96
The oxidation reaction of 2-aminophenol (OAP) to 2-aminophenoxazin-3-one (APX) initiated by 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) has been investigated in methanol at ambient temperature. The oxidation of OAP was followed by electronic spectroscopy and the rate constants were determined according to the rate law −d[OAP]/dt=kobs[OAP][TEMPO]. The rate constant, activation enthalpy and entropy at 298 K are as follows: kobs (dm3 mol−1 s−1)=(1.49±0.02)×10−4, Ea=18±5 kJ mol−1, ΔH‡=15±4 kJ mol−1, ΔS‡=−82±17 J mol−1 K−1. The results of oxidation of OAP show that the formation of 2-aminophenoxyl radical is the key step in the activation process of the substrate. 相似文献
5.
Andreas Klipp Stefan H. A. Petri Beate Neumann Hans-Georg Stammler Peter Jutzi 《Journal of organometallic chemistry》2001,620(1-2):20-31
The new chloro(cyclopentadienyl)silanes Cp′SiHyCl3−y (Cp′=Me4EtC5, y=1: 1; Cp′=Me4C5H, y=1: 2; y=0: 3; Cp′=Me3C5H2, y=1: 4 and pentachloro(cyclopentadienyl)disilanes Cp′Si2Cl5 (Cp′=Me5C5 5, Me4EtC5 6, Me4C5H 7, Me3C5H2 8, Me3SiC5H4 9) are synthesized in good yields via metathesis reactions. Treatment of 1–9 with LiAlH4 leads under Cl–H exchange to the hydridosilyl compounds Cp′SiH3 (Cp′=Me4EtC5 10, Me4C5H 11, Me3C5H2 12) and to the hydridodisilanyl compounds Cp′Si2H5 (Cp′=Me5C5 13, Me4EtC5 14, Me4C5H 15, Me3C5H2 16, Me3SiC5H4 17). Complexes 1–17 are characterized by 1H, 13C, and 29Si-NMR spectroscopy, IR spectroscopy, mass spectrometry and CH-analysis. The structures of 6, 7 and 9 are determined by single-crystal X-ray diffraction analysis. Pyrolysis studies of the cyclopentadienylsilanes 10–12 and disilanes 13–17 show their suitability as precursors in the MOCVD process. 相似文献
6.
7.
Kiyoshi Kikukawa Kazutoshi Ikenaga Kiyoshi Kono Koji Toritani Fumio Wada Tsutomu Matsuda 《Journal of organometallic chemistry》1984,270(3):277-282
Arenediazonium tetrafluoroborates (ArN2BF4 where Ar=Ph, 4-MeC6H4, 4-BrC6H4, 4-IC6H4 and 4-NO2C6H4) reacted easily with CH2=CHSiMe3 at 25 δC to give ArCH=CH2, (E-ArCH=CHSiMe3 and Ar(Me3Si)C=CH2 in excellent yields under palladium(O) catalysis. (E)-ArCH=CHSiMe3 compounds were obtained predominantly and isolated in good yields by using an excess of CH2=CHSiMe3 over ArN2BF4. Protodesilylation of the reaction mixture afforded styrene derivatives. 相似文献
8.
Study of initiation reactivity of some plastic explosives by vacuum stability test and non-isothermal differential thermal analysis 总被引:5,自引:0,他引:5
On the basis of measurements of 18 high explosives by means of the Czech Vacuum Stability Test (VST) STABIL, a relationship has been specified between the results of this test and those of Russian manometric method. The said relationship was used to predict the Arrhenius parameters (Ea and log A values) of four plastic explosives based on RDX and one high explosive based on PETN (Semtex). The slopes EaR−1 of Kissinger's equation were specified by means of non-isothermal differential thermal analysis (DTA) and evaluation of the measurement results by means of the Kissinger method. The role played by binders and plasticizers in thermal decomposition of nitramines was pointed out on the basis of relationship between the Ea values obtained from VST and the EaR−1 values obtained from DTA, both for plastic explosives, eight nitramines, Composition B and PETN. The relationships between the EaR−1 values and thermostability threshold was specified for the given group of explosives. The relationship classify some of the studied plastic explosives as belonging to nitramines with steric hindrance in the molecule (CPX, TNAZ and HNIW). The relationship between EaR−1 values and drop energies, Edr, sharply differentiates between plastic explosives and individual nitramines. From the relationship between the Edr and D2 values it was found that the increasing performance of the studied nitramines and plastic explosives is connected with the decrease in their impact sensitivity. Also specified are the approximate linear dependences between the peak temperatures of exothermic decomposition of all the explosives studied and their ignition temperatures, Tig, or critical temperatures, Tc; these dependences were applied to prediction of Tig and Tc of both the studied plastic explosives and some of the nitramines. 相似文献
9.
The photophysical properties, which vary as R is varied, of a series of [Pt(N2O2)] complexes bearing bis(phenoxy)bipyridine auxiliaries with different substituents R=H (Pt-H) (1), 4,4′-2NH2 (Pt-NH2) (2), 4,4′-2tBu (Pt-tBu) (3), 4,4′-2CN (Pt-CN) (4), and 4,4′-2NO2 (Pt-NO2) (5) are investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The solvent effects are discussed in CH2Cl2, CH3CN and CH3OH solutions, respectively, by polarizable continuum model (PCM). It is anticipated that compared with σ-donor substituents, π-acceptors have more dramatic effects on the electronic and optical properties in this series of complexes. Introduction of π-electron withdrawing substituents on bipyridine ligand will benefit the LLCT (or MLCT) and prohibit the non-radiative pathways via d–d transitions by increasing the energy gap between the HOMO–LUMO and d–d transitions. The results also reveal that the lowest-energy excitations of all complexes show blue-shifts in the polarized solution and when the polarity of the solvent increases from CH2Cl2, CH3CN and CH3OH, the low-energy broad absorption band exhibit blue-shifts. The lowest-energy excitations and photoluminescence of all complexes are dominated by π(phenoxy)→π*(bpy/NO2) (LLCT) excited state mixed with some energetically dπ (Pt)→π*(bpy/NO2) (MLCT) transition. 相似文献
10.
N. M. Klimenko K. V. Bozhenko E. V. Strunina E. A. Rykova O. N. Temkin 《Journal of Molecular Structure》1999,490(1-3):233-241
Ab initio calculations were performed for special points of the minimal energy pathways (MEP) of the nucleophilic addition reactions of the isolated H− anion, LiH molecule and Li+/H− ion pair to acetylene (A) and methylacetylene (MA) molecules, proceeding in accordance (M) and against (aM) the Markovnikov's rule. All structural parameters were optimized using the restricted Hartree–Fock (RHF) method. For the addition of H−, the 6-31++G* basis set was used and for the reactions of LiH and Li+/H− the 6-31G* basis set with the subsequent recalculation of single point energies, taking into account of electron correlation energy by means of the second-order Möller–Plesset perturbation theory at the MP2/6-31++G** level. The results of calculations demonstrate, that the energy characteristics of both M- and aM-additions with H− do not differ sufficiently (0.1–1.2 kcal/mol for the activation energies (ΔEa) and the reaction heats (ΔQ)). The substitution of the H atom by the CH3 group in A molecule results in practically the same values of ΔQ and ΔEa. On the contrary, for the LiH molecule and Li+/H− ionic pair, the M-addition is favorable (charge control). It is found that the presence of electrophile decreases the activation energy by 3–5 kcal/mol as compared with the addition of the isolated hydride ion H−. 相似文献
11.
Shohreh Nafisi Amir Sobhanmanesh Majid Esm-Hosseini Kamran Alimoghaddam Heidar Ali Tajmir-Riahi 《Journal of Molecular Structure》2005,750(1-3):22-27
Sn(CH3)2Cl2 exerts its antitumor activity in a specific way. Unlike anticancer cis-Pt(NH3)2Cl2 drug which binds strongly to the nitrogen atoms of DNA bases, Sn(CH3)2Cl2 shows no major affinity towards base binding. Thus, the mechanism of action by which tinorganometallic compounds exert antitumor activity would be different from that of the cisplatin drug. The aim of this study was to examine the binding of Sn(CH3)2Cl2 with calf thymus DNA and yeast RNA in aqueous solutions at pH 7.1–6.6 with constant concentrations of DNA and RNA and various molar ratios of Sn(CH3)2Cl2/DNA (phosphate) and Sn(CH3)2Cl2/RNA of 1/40, 1/20, 1/10, 1/5. Fourier transform infrared (FTIR) and UV–visible difference spectroscopic methods were used to determine the Sn(CH3)2Cl2 binding mode, binding constant, sequence selectivity and structural variations of Sn(CH3)2Cl2/DNA and Sn(CH3)2Cl2/RNA complexes in aqueous solution. Sn(CH3)2Cl2 hydrolyzes in water to give Sn(CH3)2(OH)2 and [Sn(CH3)2(OH)(H2O)n]+ species. Spectroscopic evidence showed that interaction occurred mainly through (CH3)2Sn(IV) hydroxide and polynucleotide backbone phosphate group with overall binding constant of K(Sn(CH3)2Cl2–DNA)=1.47×105 M−1 and K(Sn(CH3)2Cl2–RNA)=7.33×105 M−1. Sn(CH3)2Cl2 induced no biopolymer conformational changes with DNA remaining in the B-family structure and RNA in A-conformation upon drug complexation. 相似文献
12.
Catherine D. Clark Morton Z. Hoffman D. Paul Rillema Quinto G. Mulazzani 《Journal of photochemistry and photobiology. A, Chemistry》1997,110(3):285-290
The photophysics of three complexes of the form Ru(bpy)3−(pypm)2+ (where bpy2,2′-bipyridine, pypm 2-(2′-pyridyl)pyrimidine and P=1, 2 or 3) was examined in H2O, propylene carbonate, CH3CN and 4:1 (v/v) C2H5OH---CH3OH; comparison was made with the well-known photophysical behavior of Ru(bpy)32+. The lifetimes of the luminescent metal-to-ligand charge transfer (MLCT) excited states were determined as a function of temperature (between −103 and 90 °C, depending on the solvent), from which were extracted the rate constants for radiative and non-radiative decay and ΔE, the energy gap between the MLCT and metal-centered (MC) excited states. The results indicate that *Ru(bpy)2(pypm)2+ decays via a higher lying MLCT state, whereas *Ru(pypm)32+ and *Ru(pypm)2(bpy)2+ decay predominantly via the MC state. 相似文献
13.
The preparations and spectroscopic characteristics are reported of a series of (trimethylgermyl)methyl- and (trimethylstannyl)methylplatinum(II) complexes with diene and P-donor ancillary ligands, cis-Pt(CH2GeMe3)2L2 (L = PPh3 or PPh2Me; L2 = dppe or cod) and cis-Pt(CH2SnMe3)2L2 (L = PPh3; L2 =cod). Thermolysis of toluene solutions of cis-Pt(CH2GeMe3)2(PPh3)2 leads to cis-Pt(Me)(CH2GeMe2CH2GeMe3)(PPh3)2 via β-alkyl migration, after (non-rate-limiting) phosphine dissociation. Estimated activation parameters (ΔH298 K‡ = 126 ± 3 kJ mol−1, ΔS‡ = + 17 ± 7 J mol−1 K−1 and hence Δ298 K‡ = 121 ± 5 kJ mol−1) suggest that this system is more migration labile than its silicon analogue, primarily as a result of a lower activation enthalpy. While cis-Pt(CH2GeMe3)2(PPh2Me)2 reacts similarly but less readily, Pt(CH2GeMe3)2(dppe)2 is inert at operable temperatures. Thermolysis of Pt(CH2GeMe3)2(cod) generates 1,1,3,3,-tetramethyldi-1,3-germacyclobutane as the major organogermanium product, while from cis-Pt(CH2SnMe3)2(PPh3)2, 1,1,3,3-tetramethyldi-1,3-stannacyclobutane predominates. Mechanistic implications are discussed. 相似文献
14.
Colin Eaborn Anna Kowalewska J. David Smith Wlodziemierz A. Sta
czyk 《Journal of organometallic chemistry》2001,640(1-2):29-36
The new organosilicon bromides (Me3Si)2(ZMe2Si)CSiMe2Br with Z=PhO or MeS have been prepared and new spectroscopic data obtained for the previously reported compounds with Z=H, F, Br, Me, Ph, MeO or PhS. Competitions between pairs of bromides for a deficiency of AgBF4 in Et2O, with the determination of the ratio of the fluoride products by 19F-NMR spectroscopy, have led to the following approximate relative reactivities of the bromides and so to the relative abilities of the γ-Z groups to provide anchimeric assistance to the leaving of Br− in this reaction: Me, 1; Ph, 40; PhO, 3400; PhS, 5000; MeS, 7000; MeO, 54 000. In methanolysis in CH2Cl2, (Me3Si)2(MeOMe2Si)CSiMe2Cl has been found to be roughly 120 times as reactive as (Me3Si)2(PhOMe2Si)CSiMe2Cl. Combination of the results with previously available information suggests the following approximate order of ability of γ-groups Z to provide anchimeric assistance in reactions at the Si---X bonds in compounds (Me3Si)2(ZMe2Si)CSiMe2X: OCOMe>OMe>OCOCF3>MeS>PhS, PhO>N3, Cl>NCS>Ph>CH=CH2>Me. 相似文献
15.
K. Wohnrath C.A. Pessoa P.M. dos Santos J.R. Garcia A.A. Batista O.N. Oliveira Jr. 《Progress in Solid State Chemistry》2005,33(2-4):243-252
The electrochemical properties of mer-[RuCl3(dppb)(4-pic)] (dppb = Ph2P(CH2)4PPh2, 4-pic = CH3C5H4N), Rupic, in CHCl3 are governed by the formation of species such as [Ru2Cl5(dppb)2], [Ru2(dppb)2Cl4(4-pic)] and trans-[RuCl2(dppb)(4-pic)2] upon the reduction of “[RuCl2(dppb)]”. The overall behavior depends on whether Rupic is immobilized in cast or Langmuir–Blodgett (LB) films, or incorporated into a carbon paste electrode (CPE). In cyclic voltammograms, one redox process appears for LB/Rupic films and CPE/Rupic, at Epa = 0.35 V, Epc = 0.25 V vs SCE, and Epa = 0.32 V, Epc = 0.24 V vs Ag/AgCl, respectively. This redox process was ascribed to the RuIII/RuII charge transfer. For cast films the redox pair was poorly defined, with Epa = 0.27 V and Epc = 0.20 V. The reason for the difference lies in the phase separation and formation of aggregates onto ITO for the cast film, in contrast to the LB film. With aggregation, the formation of species occurring in solution is impaired for Rupic in cast films. The electrochemical properties for Rupic in LB films and incorporated into CPE allowed the electrocatalytic activity of Rupic to be exploited in sensors for dopamine and ascorbic acid. 相似文献
16.
Treatment of the dimer complex [C5Me5 (CO)2 Ru]2 (1) with HBF4 in CH2Cl2 at room temperature yields the hydrido-bridged dinuclear complex [(C5Me5)2Ru2(CO)4H]BF4 (2), and after refluxing in propionic anhydride [C5Me5(CO)3Ru]BF4 (5) is obtained, UV-irradiation of 1 in the presence of H2CHal2 (Hal = Cl, I) or trimethylphosphine leads to the formation of C5Me5(CO)2Ru-Hal (3a, 3b) or C5Me5(CO)(Me3P)RuH (4) respectively. Exchange reactions of 3a, 3b with LiAlH4, NaOMe and Me3 P give the complexes C5Me5(CO)2RuX (6a,6b) (X=H, OMe), C5Me5(CO)(Me3P)Ru-Hal (7a,7b) (Hal = Cl, I) and C5Me5(Me3P)2RuI (8). The interaction of 3b or 5 with Me3P=CH2 leads to the formation of the ylide complex [C5Me5(CO)(Me3P)-RuCH2PMe3)Cl (9) or the rutheniumacyl-ylide C5Me5(CO)2RuC(O)CH=PMe3 (10). 4 reacts with Me3P=CH2 to give C5Me5(CO)(Me3P)RuMe (11) and Me3P via the intermediate formation of the phosphonium salt Me4P[Ru(CO) (Me3P)-C5Me5]. 相似文献
17.
R. Jakubas G. Bator W. Medycki N. Pi?lewski R. Decressain J. Lefebvre P. François 《Journal of Molecular Structure》1996,385(3):207-151
The phase transitions and molecular motions of the methylammonium cations were investigated in the (CH3NH3)3Bi2Cl9 (MACB) crystal by dilatometric and dielectric measurements, and by the measurements of the 1H spin-lattice relaxation times and second moment of the 1H NMR absorptions over a wide temperature range. Structural phase transitions, weakly first order at 247 K (III ↔ II) and continuous at 352 K (II ↔ I), were detected by the dilatometric technique. The 1H NMR measurements revealed the presence of the uniaxial reorientations of the three non-equivalent methylammonium cations in the lowest temperature phase (III). 相似文献
18.
利用2-乙酰基吡啶(acpy) 和2-邻甲基苯胺在甲醇中回流反应得到新型希夫碱配体2-{1-[(2-甲基苯基) 亚氨基]-乙基}吡啶)(mpep) , 通过溶剂热法将acpy和mpep与氯化镉反应得到2种新型氯桥连一维之字链结构Cd(Ⅱ) 配位聚合物{[Cd(mpep) ]Cl2}n(配合物1)和{[Cd(acpy) ]Cl2}n(配合物2). 利用单晶X射线衍射、 核磁共振氢谱、 元素分析和红外光谱对配合物1和配合物2进行结构表征. 结果表明, 配合物1和配合物2均为一维之字链状结构. 在配合物1中, Cd与mpep配体中2个氮原子和4个氯原子配位, 呈六配位顺式八面体构型, 并通过2个Cl原子桥连形成一维之字链状结构. 在配合物2中, 中心金属Cd(Ⅱ) 与acpy中的氮原子、 氧原子和4个氯原子配位, 也呈六配位顺式八面体构型, 进一步通过Cl原子桥连相邻金属形成一维之字链状结构. 在3种不同极性的溶剂(CH3OH, CH3CN和 CH2Cl2)中, 两种配位聚合物均呈现蓝色荧光(390~433 nm) , 说明2种配位聚合物具有弱溶剂效应; 在固态室温下两种配位聚合物也呈现蓝色荧光, 最大发射波长分别为440和473 nm. 固态最大发射波长比溶液中红移的原因是分子中存在氢键, 降低了基态与激发态之间的能级差. 在室温下, 配合物1和配合物2在3种溶液和固态中均显示出较长的荧光寿命(19.08~60.20 μs) . 相似文献
19.
Manolis A. Fousteris Anna I. Koutsourea Sotiris S. Nikolaropoulos Abdelkhalek Riahi Jacques Muzart 《Journal of molecular catalysis. A, Chemical》2006,250(1-2):70-74
Various chromiumVI-catalyzed conditions have been tested to improve the oxidation of Δ5-steroids with t-BuOOH to their corresponding 5-en-7-ones. The use of PDC or the association of CrO3 with an amine as the catalyst and CH2Cl2 or PhCF3 as the solvent led usually to the best yields. A minor reaction pathway was the epoxidation of the double bond. 相似文献
20.
M. G. Voronkov V. A. Klyuchnikov L. I. Marenkova 《Journal of organometallic chemistry》1996,510(1-2):263-265
The enthalpy of formation (ΔHf0), enthalpy of evaporation (ΔHv0) and enthalpy of atomization (ΔHa) of permethylcyclosilazanes (Me2SiNH)n (n = 3, 4) and 1,1,3,3-tetramethyldisilazane (Me2SiH)2NH have been determined. The enthalpies of formation of these compounds were compared with those calculated by the Benson-Buss-Franklin and Tatevskii additive schemes. In higher permethylcyclosilazanes the energy of the endocyclic Si---N bond is 306 ± 2 kJ mol−1 (73 kcal mol−1), that is 12 ± 2 kJ mol−1 (3 kcal mol−1) lower than the energy of the acyclic Si---N bond. The strain energy of the cyclotrisilazane ring is estimated to be 10.5 kJ mol−1 (2.5 kcal mol−1), whereas the energy of the ring Si---N bond is 295 kJ mol−1 (70.5 kcal mol−1).
The thermochemical data for permethylcyclosilazanes were compared with the corresponding values for permethylcyclosiloxanes calculated from the results of previously reported studies. 相似文献